1. Field of the Invention
This invention pertains to an apparatus and method for rehabilitative exercise of a shoulder or arm injury. More specifically, the subject exercise device and method are uniquely adapted for isokinetic type exercise utilizing the patient's own body as part of the exercise system. Such isokinetic exercises include both passive and active movements.
2 Description of Prior Art
The rehabilitation of a shoulder, arm or wrist injury involves the progressive treatment of the patient through several different phases. Typically, the first phase of rehabilitation is to restore flexibility to the injured part of the body (for simplicity, general reference to the arm includes reference to the shoulder, elbow, arm or wrist). This flexibility is represented by a normal range of motion between the extremes of motion permitted for the particular part of the anatomy. For example, full flexibility of the arm would permit excursion from a lower extremity where the arm projects downward in a rearward direction through an upper extreme position.
Where injury has occurred, this range of motion or flexibility is often substantially reduced. Rehabilitation to regain flexibility is typically accomplished by passive motion wherein the injured arm is moved by an external force, such as the other arm, a physical therapist or a machine. By starting out with a restricted excursion path and gradually extending the range of motion toward each of the extreme positions, flexibility can frequently be restored.
Once the patient has the desired flexibility wherein the arm can be moved through a full range of motion without pain or further damage, the second phase of rehabilitation is initiated involving improvement of flexibility at the extremes of motion. This is a particularly dangerous part of the rehabilitation treatment because the patient is most succeptable to strains and other forms of injuries which occur when the muscles and tendons are being stretched to their limits.
None of the state of the art devices or methods of therapy are satisfactory for this second phase of rehabilitation because they lack adequate control over very slight movements which can exceed the proper range of motion and thereby cause further injury to the patient. It should be noted that very slight movement in exercises conducted at the extremities of the range of motion can cause further strain, and the mere registration of pain by the patient may be too late to prevent such injury. Furthermore, even when the patient is in control of his own exercise program, such as with the use of weights, etc., the weight may exceed the safe range and result in inadvertent injury prior to the patient's ability to recover before being subjected to excess motion by the weight being used. This uncontrolled use of weights occurs partly because of the change in tension experienced within muscles as it rotates through any given excursion path.
For example, the forces applied by a weight held in a hanging position near the waist of the patient changes substantially as the patient flexes his arm. Maximum force is applied to the shoulder when the arm is at a right angle because of the lever effect developed by the arm in that position. This variation of force applied to the shoulder can result in unexpected changes which may overpower the strength of the patient during his rehabilitation therapy.
The third phase in rehabilitation is development of strength. Typical method involve the use of free weights in which the patient starts with lighter weights and progresses to a heavier range. Again, the problem with the use of free weights is the variation in force applied to the injury as the muscle goes through its normal excursion. A preferred type of therapy would be based on isokinetic exercise in which the resistance to the muscle varies according to the demand which the muscle places on the exercise device.
During this phase of developing strength, it is apparent that the amount of weight or force subjected to the injury must gradually be increased until natural strength is returned. Obviously, this increase in weight presents a risk that excessive weight may be applied in advance of sufficient strength in the injured muscle. This is particularly true in the extremities of motion where weakness is usually greatest.
Finally, the fourth phase of rehabilitation involves development of functional activity. In the case of the arm, the activity may involve a lifting or throwing motion, or any number of natural activities which are within the customary capabilities of the patient. Currently, there is very little practical equipment available to assist the patient in functional therapy. For example, the simulation of a throwing motion is very difficult with machines. Any machinery which has been developed to simulate such functional activity tends to be very expensive, cumbersome, large in size and complicated to operate. Where the patient attempts to enter actual participation, in the functional activity (such as sports, lifting, strenuous work etc.) renewed injury is frequent because of carelessness in avoiding activity beyond his capability.
Even in the case of expensive orthopedic equipment designed to provide somewhat of an isokenetic exercise, the equipment is not ideal for the extremes of motion. Therefore, it will be apparent to those skilled in the art that the current methods of rehabilitation fall short of meeting the needs of the typical transition in therapy to restored health. Even more significant, no single therapy device or method is adequate to meet the needs of each of the respective stages of rehabilitation. For example, a physical therapist may be helpful in restoring flexibility to the injury; however, his contribution in functional therapy is greated reduced. Where the patient assumes his own exercise program, risk of excessive strain is constantly present because of inexperience or an anxiety to accelerate the rehabilitation process. Finally, none of the prior art methods or devices are well suited for therapy in the extreme ranges of motion because of their lack of sensitivity or fine tuning to the actual muscle strength or weakness in those extreme positions.